The invention relates to electrical tools, and more particularly to a tensioning nut to secure a disk-shaped tool on a threaded spindle of an electrical tool.
Electrical tools, particularly hand tools, have been equipped with a braking device so that the threaded spindle thereof quickly comes to a stop when the electrical drive is shut off. Such devices exist on circular saws and right-angle grinders to stop the saw blade or grinding disk quickly. Particularly with right-angle grinders and their rapidly-spinning grinding disks, there is the problem with rapid spindle braking of reducing the angular energy of the grinding disk, whereby the angular momentum of the grinder disk is directed in opposition to the tightening direction of the tensioning nut securing the grinder disk. Therefore, this tensioning nut must be one with which the grinder disk is secured to the threaded spindle of the electric hand tool.
Right-angle grinders with a run-out brake have been developed to reduce the hazard to the user. For this, the spinning grinder disk is braked to a stop very quickly after the device is switched off. Since the braking devices act on the tool spindle, there exists the danger that, in spite of a stopped tool spindle, the grinder disk continues to spin because of its angular energy, turning the tensioning nut connected with it against its tightening direction through friction. A conventional tensioning nut may thus loosen from the threaded spindle of the right-angle grinder, resulting in release of the rotating grinder disk from its mount on the threaded spindle.
Special tool tensioning devices have been developed for braked run-out right-angle grinders in order to be able to transfer the braking force on the threaded spindle to the grinder disk. Publication EP 0 459 697 A1 describes a tensioning nut that works together with a pressure flange attached to the threaded spindle of a right-angle grinder so that it may not rotate; the grinder disk is tensioned between the pressure flange and the tensioning nut. The tensioning nut may rotate only in the tightening direction relative to the pressure flange because of the so-called spinning block, and loosening the tensioning nut in the direction opposite to the rotation direction is only possible after the limitation of the block is manually released. For this, a part of the tensioning device must be displaced axially, which complicates its design and makes it vulnerable to failure.
Publication DE 43 37 023 A1 describes a tensioning nut for a braked run-out right-angle grinder that includes a pressure ring mounted in a nut body that is held within the nut body by a thread whose rotational direction is opposite to that of the thread between the nut body and the threaded spindle. When the grinder disk exerts torque on the pressure ring, it moves by rotation away from the grinder disk without transferring its rotational motion to the nut body, whereby release of the entire tensioning nut from the threaded spindle is prevented.
Publication DE 41 31 514 A1 describes a tensioning device that is also provided for a hand tool with spindle brake, particularly for a right-angle grinder. Here, either the outer tensioning nut or the inner pressure flange is provided with additional mechanical auxiliary supplement such as pressure members resting on spiral-shaped wedge-shaped surfaces by means of which the tensioning force is even increased during the braking of the devices threaded spindle. For this, a matching threaded spindle must be used, which is why the entire tensioning device is complex, and cannot be used on a grinder disk of conventional design.
Publication DE 41 22 320 A1 shows a tool-securing device for right-angle grinders with a braking device that is also complex because there is a coaxial shell displaceable along the threaded spindle that is provided at the machine end with an actuation lever, and the other end is connected with a pressure flange resting on the grinder.
Publication DE 195 09 147 C1 describes a tensioning nut to secure a disk-shaped tool for which an axial roller bearing is positioned between the nut body and the pressure ring along with a spring to transfer rotational motion. This design merely serves to function as a friction coupling when a limiting torque value is exceeded.
Publication EP 0 615 815 A1 describes a tool tensioning device on a right-angle grinder for which the tensioning nut rests against the threaded spindle by means of a blocking mechanism in the direction opposite its tightening direction in order to release the tensioning nut when the threaded spindle is driven in the opposite direction to the working direction.
One goal of the present invention is to create a tensioning nut to secure a disk-shaped tool to a threaded spindle of a run-out braked electrical hand tool that has a simple design, and further, which prevents unintentional loosening of the tool from the threaded spindle and which requires no design adaptation measures for the threaded spindle or the disk-shaped tool. The tensioning nut of the present invention thus may be used instead of a conventional tensioning nut.
The invention features a tensioning nut to secure a disk-shaped tool to a threaded spindle of an electrical tool with run-out brake. The nut includes a nut body that may be threaded onto the threaded spindle and removed from it, and a pressure ring positioned coaxially on the nut body and tensioning the tool. The nut also includes an axial bearing positioned between the pressure ring and the nut body, and a blocking disk which prevents rotation and rests in the nut body. The disk includes at least one blocking body positioned so that a disengagement exists between the nut body and the blocking disk in the tensioning direction, and engagement exists between the nut body and the blocking disk in the opposite direction, whereby the nut body and blocking disk rotate together.
A particular advantage of a tensioning nut of the present invention is that the nut body may be rotated in the tightening direction of the tensioning nut with respect to the pressure ring. The axial bearing serving as pressure bearing between the nut body and the pressure ring allows this relative rotation, while the blocking mechanism consisting of a blocking wheel and a blocking body represents a uni-directional coupling that allows rotation of the nut body relative to the pressure ring in only one direction, namely the tightening direction. Tightening the tensioning nut may be performed either manually or using a tool, and the pressure ring resting on the disk-shaped tool does not rotate with it. As a counter-bearing to tighten the tool, a conventional, inner pressure flange may be provided on the tool mount of the threaded spindle that rests on the threaded spindle in a fixed axial position with a friction fit and/or shape fit. In the working direction of the threaded spindle, which is opposite the tightening direction of the nut body, transfer of rotation between the pressure ring and the nut body results, with which two effects are connected. If the rotating tool is braked by the work process and thus torque is transferred from the pressure ring of the tensioning nut to the tool, then the relative limitation of the pressure ring is transferred to the nut body in the working direction, whereby the driven threaded spindle may rotate relative to the nut body in the tightening direction, tightening the tensioning nut further. On the other hand, the torque caused by the mass of the disk-shaped tool during run-out of a braked threaded spindle is merely transferred to the pressure ring of the tensioning nut and not to the nut body. If the tool resultantly rotates relative to the threaded spindle, which should not occur, then the rotation is not transferred to the nut body of the tensioning screw by the pressure ring rotating with the tool by friction. The tensioning force transferred from the pressure ring remains unchanged so that the friction present in the entire tool mount with respect to the tool is sufficient to bring the tool to a stop by means of the threaded spindle. Intentional loosening by the user of the tensioning nut by gripping the nut in a normal manner is independent of this.
Advantageous embodiment properties of the invention may be taken from the dependent claims. It is important to note that the present invention is not intended to be limited to a device or method which must satisfy one or more of any stated or implied objects or features of the invention. It is also important to note that the present invention is not limited to the preferred, exemplary, or primary embodiment(s) described herein. Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention, which is not to be limited except by the following claims.